1. Field of the Invention
This invention relates to an improvement of a rack and pinion type steering apparatus of a motor vehicle such as an automobile with a bushing sleeve for slidably supporting a steering gear rack within a steering gear housing.
2. Description of the Related Art
In a rack and pinion type power steering apparatus of an automobile, when a pinion shaft coupled to a steering wheel rotates accompanying with the rotation of the steering wheel, a steering gear rack engaged with the pinion shaft is shifted right and left within a steering gear housing, thereby to steer wheels. Various kinds of proposals have been made for a bushing sleeve to slidably support the steering gear rack in the steering gear housing of the rack and pinion type power steering apparatus as above-described (Japanese Utility Model Laid-Open No. 54-69532, Japanese Patent Laid-Open No. 61-13019).
FIG. 1 is a cross section of a conventional bushing sleeve in using, and FIG. 2 is an enlarged cross section taken along the line II--II of FIG. 1. In the drawings, numerals respectively represent: 21 a steering gear housing; 22 a steering gear rack; 23 a pinion shaft; and 24 and 25 busing sleeves.
The steering gear rack 22 is slidably supported at two points by respective bushing sleeves 24, 25 within the steering gear housing 21 which are away from the pinion shaft 23 and in the vicinity of the pinion shaft 23.
The busing sleeves 24, 25 are formed circular of synthetic resin. Regarding one bushing sleeve 24, as indicated in FIG. 2, it has circular arc contacting areas 24a in contact with the inner surface of the steering gear housing 21, and noncontacting areas 24b which are so flat as to be cut off on the outer surface, where the contacting area 24a and noncontacting area 24b are alternately arranged. A catching projection 24c is formed approximately at the center of each contacting area 24a. The bushing sleeve 24 in the structure as above is inserted between the housing 21 and steering gear rack 22, so that each catching projection 24c is fitted into a corresponding hollow 21a of the housing 21.
In the meantime, since a space 26 is formed in the conventional bushing sleeve 24 between the noncontacting area 24b of the bushing sleeve 24 and the inner surface of the housing 21, so as to absorb the dimensional errors and to secure the circulation of air, the noncontacting area 24b is rendered to be thin and accordingly low in rigidity, the steering gear rack 22 may be deflected at a part corresponding to the space 26 when a radial force acts to the rack 22, with generating a hitting noise. Moreover, the rigidity of the joint of the steering gear rack 22 and pinion shaft 23 is low in the conventional structure.